Empty container or box with fixed side walls requires a lot of space for storing, and therefore, the existing container includes collapsible side walls, thereby reducing the space occupied by the container during transport. Most of these collapsible containers comprise a base in form of rectangular plate structure, wherein the collapsible side walls are coupled to the edges of the base by hinges. The side walls may be interlocked when the container stay erected, usually through engaging the latch of one side wall with the hook of another side wall.
For many containers, the side walls are configured to be higher than half of the width of the base, thus the opposite side walls will be overlapped when they are folded towards each other. Therefore, the side wall which is folded later will go beyond the edge of the side wall which is folded first and will be not parallel to the base but angled. When pluralities of containers are overlapped, the upper side walls will he bent and deformed or damaged with time elapses. For such containers, another drawback is that several containers can not be stacked in a stable way.
To solve this problem, one solution is to connect the side walls to the rods of the base at different height respectively. However, the height of the opposite side walls are different, which leads to increase the cost of manufacturing and maintaining. Further, the workers must pay more attention during the operation which will affect the efficiency to some extend, since the folding work should be executed sequentially. It needs a more advanced alternative solution to solve this problem.
U.S. Pat. No. 5,938,059A disclosed a solution to solve the above problems. One side wall and the opposite side wall may overlap each other in a manner that the side walls are placed parallel to the base and the folding order is not limited through an oval hole provided on the base and a pin the base of the match, the pin being able to move up and down in the oval hole within a distance. This invention solves the problem of folding container to a certain extent. Also, the side walls of container are same with each other. However, it needs additional pins or tubes as pivot shafts and tools should be used to operate the pivot shafts when assembly or disassembly the side walls, which will lower the efficiency.
WO2005102850A1 proposed a more advanced solution with respect to the above solution. The solution of WO2005102850A1 optimizes the assembly method of the side walls and the base. The solution of WO2005102850A1 comprises a side wall having two specific projections with widths (w1, w2) respectively, the base having a recess with an opening. When the side wall is rotated to 45 degrees with respect to the base, the minimum width w2 of the projection may exactly pass through the opening of the recess so that the side walls and the base are assembled or disassembled. The side walls and the base may be assembled or disassembled without tools according to WO2005102850A1.
However, both application need an additional mechanism for moving the erected side walls up and down when lock the side walls to the base, and it is troublesome for assembly or disassembly the side walls according to U.S. Pat. No. 5,938,059A. Further, there is a large space for moving the pivot shafts during the rotation of the side walls according to WO2005102850A1, which leads to a poor operating experience.